1. Field of the Invention
The present invention relates to a sealing system between a relatively rotating element and a stationary element, possibly a drill pipe and a wash pipe.
2. Related Art
Drilling is done by having a rotating drill pipe extending between the drill bit and the surface facility. The surface facility is either on land, on a floating vessel, a platform or other kind of installation. There will naturally be relative rotation between the drill pipe and the surface facility. At the same time there are fluid lines in the drill pipe which need to be connected to equipment on the surface facility for transfer of a fluid from a fluid path in the drill pipe to the surface facility. One possible solution for this is to provide swivel means in the connection between the drill pipe and the surface facility. Such swivel means may for instance be a so-called washpipe connected to the drill pipe. These swivel means should also prevent leakage of fluids to the environment and preferably be easy to use, assemble and repair. The swivel means also has to withstand high pressure and high speed drilling with the associated extensive abrasion and wear in the connection between the relatively rotating elements.
There is known a washpipe assembly for a standard drill pipe where the system includes hydrodynamic seal lubrications where each seal has a dynamic sealing surface incorporating a wavy hydrodynamic inlet and a non-hydrodynamic exclusionary corner, pressure staging between the hydrodynamic seals where the drilling fluid pressure is divided among three pressure retaining seals, exposing each one to only a fraction of the pressure, where each sealed chamber is independently pressurized by a lubrication cylinder (lubricator energized by the drilling fluid pressure and pivoting articulation), as described in the paper IADC/SPE 59107 “A new hydrodynamic Washpipe Sealing system. Extends Performance Envelope and Provides Economic Benefit” by Morrow, Drury, Dietle and Kalsi. Such an assembly will enable it to withstand significantly higher pressures and surface speeds compared with conventional units.